Yes, kids are most definitely back in school this week, and apparently for the weekend, too. You can always tell when the shift happens as the summer box office goes from being a thing to basically a slow crawl to Labor Day when the season officially ends. While at least one of the new films this week can declare victory over the others, none of them can really declare themselves a winner. The only ones worthy of bragging rights this week are Marvel, James Gunn and the entire crew of Guardians of the Galaxy that helped make it the clear winner in this summer's box office.

A Dark Time in Sin City

Before we break down the praise of Guardians, the lead story this week is another sequel falling flat on its face. Like Dwight McCarthy falling out a window down a couple stories on to concrete and requiring a new face, Sin City's old one was not enough to draw any interest from even the fans that made the 2005 film a hit. Nine years of waiting turned a $29.1 million opening into $7 million. That's not good.

Robert Rodriguez has gone from the wunderkind that turned a $7,000 budget into the career launcher that was El Mariachi into the guy that has probably cost Harvey Weinstein more money than anyone. The initial Sin City and the first three Spy Kids notwithstanding (his four highest grossers), Rodriguez was also part of the Grindhouse debacle, budgeted at $67 million with his pal Quentin Tarantino and now Sin City: A Dame to Kill For, budgeted at around that much by himself. Even if the film manages to procure the same $84 million overseas, it has a very good shot at challenging Hercules as the biggest live-action flop of the summer.

Should I Stay or Should I Go?

Warner Bros.' If I Stay would probably feel better about itself if it had taken the number one slot overall this weekend, but its $16 million should be good enough to make it a minor hit for a studio that could use a major one. Budgeted at just $11 million (behind only The Purge: Anarchy for the smallest budget for a 2000-plus-screen release this summer) the film opened better than last week's The Giver and may hold decently for a late-summer weepie. Overall not a bad opening on the weekend just before Labor Day, which is not something that can be said by everybody.

Since 2005 these are the best openers on the pre-Labor Day weekend. (*The Mortal Instruments and Hit and Run started the Wednesday before.)

The Final Destination ($27.4), Takers ($20.5), The Last Exorcism ($20.3), Invincible ($17.0), If I Stay ($16.35), Halloween II ($16.34), The Brothers Grimm ($15.0), The House Bunny ($14.5), Death Race ($12.6), Colombiana ($10.4), Mr. Bean's Holiday ($9.88), War ($9.82), The Mortal Instruments: City of Bones ($9.3*), When the Game Stands Tall ($9.0), The World's End ($8.8), Don't Be Afraid of the Dark ($8.5), The Nanny Diaries ($7.4), You're Next ($7.0), Beerfest ($7.03), Our Idiot Brother ($7.01), Sin City: A Dame to Kill For ($6.5), The Cave ($6.1), Premium Rush ($6.0), Idlewild ($5.7), Hit and Run ($4.5*)

We had to go past 10 and even 20 titles to fit this weekend's Sin City on that last, but If I Stay (if estimates hold) nestled in there at fifth place and that's good news for a studio that has not had a true hit since Godzilla back in May. On the other hand, Sony's three losers in a row (Think Like a Man Too, Deliver Us from Evil, Sex Tape) are now as bad as Warner Bros.' five, but the studio's When the Game Stands Tall trailed behind the openings of MillionDollar Arm, Draft Day and even last year's Formula One drama Rush. If the fame fades quickly and fails to live up to the pithy U.S. grosses of those films, Sony could be looking at its fourth straight loser. But at least it opened better than Sin City.

Tales of the Top 10 (or How Guardians of the Galaxy Is Number One)

For the first time since the first weekend of the year when Frozen did it, a film has leapt back into the number one slot after multiple weeks in release. Ninja Turtles had held on to the top spot at the box office for the past two weeks, but the Guardians of the Galaxy are back in front in their fourth week of release. It didn't take until August 25 or 26 as predicted last week for James Gunn's film to be the top summer film in the U.S -- it only needed the weekend with another fantastic hold, is a few days away from being the highest U.S. grosser of 2014 and it now has a shot to do what no film has ever done opening between July 21 and November 8. $300 million is a real possibility which would give this summer (the first since 2006 likely to not break $4 billion) a real bright spot.

The numbers down the rest of the list are not as sunny. Paramount's Teenage Mutant Ninja Turtles will be breaking into the summer top 10 this week but is still about $156 million away from breaking even. Fox's Let's Be Cops had a decent hold and is now around $45 million, but will need about another $45 million to give Fox that perfect summer. Unlike previously thought, The Giver will face no challenge from Sin City when it comes to being the Weinstein's highest U.S. grosser this year. But right on target, Into the Storm is still a big flop for Warner Bros. On the bright side, though, Disney's The Hundred-Foot Journey continued to make a small decline down the top 10 and will be outgrossing Million Dollar Arm by next weekend.

Movies.com, the ultimate source for everything movies, is your destination for new movie trailers, reviews, photos, times, tickets + more! Stay in the know with the latest movie news and cast interviews at Movies.com.